Responses of macrophages against Aspergillus fumigatus – insights in known and unknown mechanisms
BERGES J. 1, SOLTAN-ESMAEILI D. 2, BITTERER K. 1, FLAMANN C. 1, VOELKL S. 1, KRUEGER R. 3, MUSELLA L. 4, VERA J. 4, BOETTCHER M. 5, MOUGIAKAKOS D. 5, KRAPPMANN S. 2, MACKENSEN A. 1, BRUNS H. 1
1 Department of Internal Medicine 5, University Hospital Erlangen, Erlangen, Germany; 2 Institute of Microbiology – Clinical Microbiology, Immunology and Hygiene, University Hospital Erlangen and Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany; 3 Department of Nephrology and Hypertension, University Hospital Erlangen, Erlangen, Germany; 4 Department of Dermatology, University Hospital Erlangen and Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany; 5 Department of Hematology and Oncology, Otto von Guericke University, Magdeburg, Germany
Contact with Aspergillus (A.) fumigatus is normally not harmful for healthy individuals – for immunosuppressed patients, e.g. after hematopoietic stem-cell transplantation (HSCT), this can lead to fulminant infections and death. In our experiments, we aimed to define relevant mechanisms for the macrophage’s response against A. fumigatus in healthy and post-HSCT individuals. For all assays, human blood derived macrophages were used. These were generated from blood by PBMC isolation with density gradient and M-CSF stimulation. As it is already described that the ROS response is essential to defend infections with A. fumigatus, we investigated the impact of conidia, swollen conidia and germlings and showed, that the presentation of immunogens as given by germlings, is essential to elicit secretion of ROS by mitochondria. Additionally, contact and phagocytosis of fungi, impacts the metabolism of macrophages. We showed, that co-incubation of macrophages and morphotypes causes increased glucose uptake. For analyses of signaling pathways, macrophages were co-cultured with fungi. After co-incubation cells were lysed and a total RNA sequencing was performed. A hallmark pathway analysis revealed significant upregulations in inflammatory response, TNF and interferon signaling. Interestingly, we detected that IFN as well as IFN signaling was upregulated by the contact with germlings. Type I interferons are mainly known from immune responses against viruses and bacteria. Whether they are important for the response against fungi, is still a matter of debate. We also showed an influence of fungi on Type I interferon response. With our assays, we get some first insights in the effects of A. fumigatus on human macrophages, and their immune response. Upregulation of pro-inflammatory signaling pathways, increased ROS production and glucose uptake, are the main effects measured in our experiments. In subsequent experiments, we aim to compare these effects between healthy and post-HSCT individuals, to elucidate why their response against fungi is impaired.